Midterm 3 - Lecture 22

Question 1

What happens to sperm in the vagina?

Answer 1

• retrograde loss of sperm
• phagocytosis
• entrance into the cervix

Question 2

What happens to sperm in the cervix?

Answer 2

• “privileged pathways” of sperm movement
• removal of non-motile and abnormal sperm

Question 3

What happens to sperm in the uterus?

Answer 3

• capacitation initiated
• phagocytosis; majority of sperm attacked and defeated

Question 4

What happens to sperm in the oviduct?

Answer 4

• capacitation completed
• phagocytosis

Question 5

What happens to sperm during fertilization?

Answer 5

• acrosome rxn
• sperm binds to and penetrates oocyte
• male and female pronuclei develop
• zygote formed

Question 6

What are the estrogenic effects on the reproductive tract?

Answer 6

• increase blood flow
• increase leukocytes
• increase mucosal secretion
• increase growth of uterine glands
• increase smooth muscle tone (gamete transport)
• genital swelling

Question 7

What do leukocytes prevent? When is there an increase?

Answer 7

• prevent infection
• within 6-12 hours after the introduction of sperm into the uterus there is a large infiltration of neutrophils from the uterine mucosa into the uterine lumen

Question 8

What is the role of the cervix?

Answer 8

• the cervix is a barrier to sperm transport, but also plays a role in sperm selection

Question 9

How does cervical mucus vary in form and fxn?

Answer 9

1. Sialomucin
   - low viscosity mucus found within the cervical crypts (folds of the cervix surface)
   - sperm that work their way into the cervical crypts are able to move through to the sialmucin and are moved towards the uterus
2. Sulfomucin
   - high viscosity mucus found at the ends of the cervical folds
   - sperm that remain in the cervical lumen are stuck to the sulfomucin and do not enter the uterus

Question 10

What are viable sperm better able to gain access to?

Answer 10

privileged pathway

Question 11

What is sperm capacitation?

Answer 11

• the process whereby sperm acquire fertility through interactions with the female reproductive tract

Question 12

Are ejaculated sperm able to fertilize an oocyte?

Answer 12

ejaculated sperm are not yet able to fertilize an oocyte; gain full ability to fertilize once they have been exposed to appropriate factors/enviro

Question 13

What are the steps of sperm capacitation?

Answer 13

• in the epididymus “egg-binding proteins” are added to the sperm head membrane that allow them to bind to an oocyte
• heads of ejaculated sperm are coated with de-capacitation factors that mask egg-binding proteins
• capacitation factors produced by the female repro tract remove decapacitation factors
• exposed egg-binding proteins able to interact with oocyte and initiate fertilization (acrosome rxn)

Question 14

What are the 3 events leading to fertilization?

Answer 14

1. Hyperactive motility
   - change from linear to rapid “figure-8” like movement
2. Binding to the Zona Pellucida
3. Acrosome Rxn

*only capacitated sperm are able to achieve these milestones

Question 15

What 3 glycoproteins does the zona pellucida consist of?

Answer 15

1. ZP1 - structural protein
2. ZP2 - structural protein
3. ZP3 - binds to proteins on the sperm membrane

Question 16

What do sperm oocyte binding proteins contain?

Answer 16

2 zona pellucida binding sites
1. primary zona binding region (ZBR)
2. acrosome reaction promoting region (ARPR)

Question 17

What is the acrosome?

Answer 17

• membrane-bound lysosome containing hydrolytic enzymes required for penetration of the oocyte zona pellucida at fertilization

Question 18

Acrosome rxn

Answer 18

• plasma membrane overlying the acrosome fuses with the outer acrosomal membrane
• fusion of the 2 membranes leads to vesiculation that allows for the release of the acrosomal enzymes

Question 19

6 sequential steps in fertilization

Answer 19

1. • acrosome-reacted sperm penetrates the Zona Pellucida
2. • sperm enter the perivitelline space and bind to the vitelline membrane
   • zona pellucida undergoes biochemical changes to prevent other sperm from penetrating = zona block
3. • sperm is engulfed by oocyte cytoplasm and passes through the vitelline membrane
   • additional alteration in oocyte membranes (vitelline block) is evoked to prevent other sperm from entering
4. • cytoplasm shrinks
   • second polar body pushed into the perivitelline space
   • DNA decondenses to form the Male and Female Pronuclei
5. Syngamy occurs = male and female pronuclei merge

6.
- single diploid (2N) nucleus forms and fertilization is complete to give a zygote